swh:1:snp:ff0951ca787d0b7f47dc2335f47fed43820a6324
Tip revision: 4b519f6c36e35e4b0c9d2e052a1710b5a42e0eda authored by Venkatraman E. Seshan on 13 September 2011, 00:00:00 UTC
version 0.9.8
version 0.9.8
Tip revision: 4b519f6
roc.curve.Rd
\name{roc.curve}
\title{Empirical ROC curve}
\alias{roc.curve}
\alias{print.roc.curve}
\alias{plot.roc.curve}
\alias{lines.roc.curve}
\description{
Computes the empricial ROC curve for a diagnostic tool.
}
\usage{
roc.curve(marker, status, method=c("empirical"))
\method{print}{roc.curve}(x, \dots)
\method{plot}{roc.curve}(x, \dots)
\method{lines}{roc.curve}(x, \dots)
}
\arguments{
\item{marker}{the marker values for each subject.}
\item{status}{binary disease status indicator}
\item{method}{the method for estimating the ROC curve. Currently only
the empirical curve is implemented.}
\item{x}{object of class roc.area.test output from this function.}
\item{...}{optional arguments to the print, plot and lines functions.}
}
\value{a list with the following elements
\item{tpr}{true positive rates for all thresholds.}
\item{fpr}{true positive rates for all thresholds.}
\item{marker}{the diagnostic marker being studied.}
\item{status}{binary disease }
The "print" method returns the nonparametric AUC and its s.e.
The "plot" and "lines" methods can be used to draw a new plot and add
to an existing plot of ROC curve.
}
\details{
The computation is based on assuming that larger values of the marker
is indicative of the disease. So for a given threshold x0, TPR is
P(marker >= x0|status =1) and FPR is P(marker >= x0|status =0). This
function computes the empirical estimates of TPR and FPR.
}
\examples{
g <- rep(0:1, 50)
x <- rnorm(100) + g
y <- rnorm(100) + 1.5*g
o <- roc.curve(x, g)
plot(o)
lines(roc.curve(y, g), col=2)
}